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DRG: Deutsche Rheologische Gesellschaft
DRG 12: Poster Strukturierte Materialien
DRG 12.5: Poster
Tuesday, March 2, 1999, 14:00–16:00, Foyer
Viscoelastic behavior of polymer melts tethered to the air/water interface — •Clarisse Luap and Werner A. Goedel — Max-Planck-Institut für Kolloid- und Grenzflächenforschung,
Rudower Chaussee 5 , D-12489 Berlin.
We present a new experimental approach to get some more insight into the
dynamics of
polymer chains tethered by one end to an interface. We investigate the
linear viscoelastic
behavior of solvent-free polymer brushes as monolayers at the air/water
interface,
depending on the surface concentration and chain length.
These brush-like monolayers, 20 to 50 nm thick, are obtained by spreading
hydrophobic
polymers with a hydrophilic head group onto the water surface[1]. The
tethering density
can be easily varied by lateral compression of the film with the movable
barrier of a
Langmuir trough. Their linear viscoelastic properties are determined
directly at the
air/water interface by applying a small amplitude oscillatory shear flow
within the
interface plane.
We will present here our results obtained on monolayers of polyisoprenes
terminated by a
sulfonated head group. When increasing the chain length, we observe a
transition from a
liquid-like to a temporary network behavior typical of an entangled polymer
melt. Their
zero shear viscosity as well as their terminal relaxation time increase
significantly when
increasing the tethering density. Both quantities are 2 to3 orders of
magnitude higher than
those of a bulk polymer melt of equivalent molecular weight.
[1] R. Heger, W.A. Goedel, Macromolecules 1996, 29, p8912.